<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        .active {
            color: red
        }
    </style>
</head>
<body>

<div id="app">
    <ul>
        <li v-for="(item, index) in movies" 
            :class="{active: currentIndex === index}" 
            @click="liClick(index)">
            {{index}}.{{item}}
        </li>
    </ul>
</div>

<script src="../js/vue.js"></script>
<script>
    const app = new Vue({
        el: '#app',
        data: {
            movies: ['海王', '海贼王', '加勒比海盗', '海尔兄弟'],
            currentIndex: 0
        },
        methods: {
            liClick(index) {
                this.currentIndex = index
            }
        }
    })
</script>

</body>
</html>